A conventional blade tip geometry of a blade part 1 of a rotating blade of a turbomachine, such as a gas turbine, for example, an aircraft engine, is shown in FIG. 1. The blade part 1 has a blade tip 2, which extends in the direction of a primary flow of a leading edge 4 to a trailing edge 6 of the blade part 1 and runs into an abradable layer 10 on the stator side during operation. The abradable layer 10 here is an abradable silicone layer, the layer loss thereof being determined by mechanical action during the rubbing against the blade tip 2. During the rubbing, the blade tip 2 pushes a “pile of silicone” in front of it until the tensile strength of the silicone material is reached and the silicone material breaks apart. The silicone particles that have been released increase still further the breaking apart of the layer beyond the actual degree of rubbing. A parasitic gap loss 12 is established thereby, which leads to an unwanted enlargement of an operating gap and thus to loss of efficiency and pump limit losses. In order to improve the running-in behavior, it is known to introduce peripheral grooves in the abradable layer. The introduction of peripheral grooves, however, complicates manufacturing techniques.
It is known from WO 2011/002570 A1 to provide blade tips of rotating blades with a cutting edge on the side of the leading edge and additionally to permit the blade tip to slope radially inward in the direction of the trailing edge. In operation, the cutting edge is positioned toward a rubber-like abradable layer on the stator side in such a way that an operating gap is basically formed between the rotating blades and the abradable layer. Now, if the blade tip runs into the abradable layer for a short time, then a defined abrasion of the abradable layer should result by means of the cutting edge. In this way, a reduction in the load on the blade should be achieved predominantly, since the layer particles abraded by the cutting edge should not remain adhered to the blade tip. Additional prior art is known from WO 2011/157927 A1, WO 2012/163337 A1, EP 1 529 962 A2, US 2007/020101 A1, EP 2 444 592 A1 and from EP 2 412 927 A1.